In recent years, with the development of display technology, portable terminals such as mobile phones and tablet computers are extremely popular. However, as portable terminals such as mobile phones and tablet computers have increased in size, these terminal devices are not easy to carry.
A foldable display device can solve the problem that it is not easy to carry. The display screen included in the foldable display device is a flexible display screen. However, when the foldable display device is folded, the radius of curvature of the folded portion of the flexible display screen may be close to the critical radius of curvature of the flexible display screen, or even less than the critical radius of curvature of the flexible display screen, and thus the display may be broken.